Currently, for example to help researchers attempting to evaluate the performance, mechanisms of operation and safety of new chemical entities, as is generally required to obtain regulatory approval of the use of such target compounds in commerce, radiolabelled analogues are prepared and employed. Often this involves the in vivo administration of a radiolabelled version of the so called tracer compound to help understand the distribution, flux, metabolic fate and tissue concentration of the compound during the course of preclinical and environmental studies. Various analytical techniques allow the researcher to know how much of and over what period of time the applied tracer compound is excreted. Just as importantly, the metabolites can be traced and measured to determine if safety issues might exist as a result of administration of the compound.
The label of choice is commonly 14C, which replaces one or more of the 12C atoms in the molecule under study. The radioisotope is rare in nature so its presence can readily be attributed to the labelled compound under study. Half-life of the isotope is long enough that there is no concern regarding the possible biological effect of its presence and it can be inserted into the carbon frame work of the target compound without altering its chemical structure. However, there are numerous problems associated with the use and handling of radiolabelling isotopes. The supply of radiolabelled raw materials is limited and their cost is high. Such isotopes are tightly regulated and disposal of waste materials is also regulated and expensive. While the half-life of 14C for example is extended, the energy related to its decay can lead to radiolytic instability of the candidate compound causing a reduction in purity with time. Thus a need exists for an alternative to the use of radiolabelled compounds to meet at least a portion of the research and regulatory requirements surrounding the development and commercialization of new, biologically active compounds for use as pharmaceuticals, agrochemicals, veterinary compounds and the like.